Drill Hole Interval Calculator

The Drill Hole Interval Calculator that Exploration Insights and Corebox have jointly developed is designed to provide you with a means of estimating the grade of drill hole intervals between the “highlights” of a longer assay interval.

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How to use this calculator

This calculator is a first pass tool for determining what might be ore and what might be waste. That determination (ore vs. waste) has enormous implications regarding the exploration potential (the size) and eventual value of a prospective property.

By knowing the average grade of the excluded
material we can tell if the company has been pushing high grade assays into very low grade rock (smearing) or if the long interval is actually representative of the entire quoted drill interval.

In a mining operation, every tonne of rock moved costs money. That means there are effectively only two rock types the novice investor needs to know about: ore and waste. Ore makes money and waste does not. It therefore follows that a prime objective of any mining operation is to mine as little waste as possible. Commit this to memory: “A mine is a terrible thing to waste”.

Generally, narrow mineralized intervals are best mined using selective underground or open pit methods, while broad intervals are best mined using bulk mining methods. As a rule of thumb, selective mining costs more than bulk mining but is less expensive to implement, while bulk mining is relatively inexpensive but requires high capital costs to get underway.

Here’s how it works

Often news releases that announce drill results report a long interval grading “X” grams per tonne gold (or any metal) over “Y” meters. The Y interval may contain smaller, higher grade intervals within; this is generally indicated by a statement such as: “Including __ grams per tonne gold over ___ meters.” Although this is useful information it only tells half the story. We also need to know what the rest of the interval grades when the high grade intervals are excluded. Would the excluded interval make money (ore) or lose money (waste) if it were mined?

To use our Residual Grade Calculator, simply fill in the data for the long interval and then the smaller or “including” intervals. You are left with the average grade of the drill interval excluding the higher grade sections. If the company has posted the results on Corebox you will be able to visually walk through the property section by section or view it in 3-D. Putting this data into geologic and economic context requires experience and understanding - that is what Exploration Insights is all about.